The invention is related to the field of passive alignment, and in particular to precision-parallel alignment of surfaces brought in close proximity.
Alignment of angle between two surfaces brought into close proximity is critical in most nanomanufaeturing applications. As an example, tilt errors between a patterned tool and substrates in stamping applications such as micro-contact printing and hot-embossing can adversely affect uniformity of pattern replication. The micro-hot-embossing process is a type of forming used for creating polymer microfluidic channels. In this setup, the tool needs to align itself with the sample to create the 200 μm deep channels. Across a 1″ wide area of the sample, with a 5-10% tolerance in channel height, approximately 400 μrad angular alignment is needed.
Other examples include small-scale gaps for applications in medical diagnostics, where a precision-parallel separation in the sub-100 nm to μm has to be achieved. Also, a programmable gap filter is designed and controlled for biologically active molecules.
Flexures have been used extensively in the prior art for positioning and alignment. Six degree-of-freedom flexure-based positioning and alignment fixtures had been designed. Passive alignment in robotic applications with flexure elements has also been used. A flexure-based alignment with conformal contact for step and flash imprint lithography has been designed. While the above technologies focused on passive alignment, none examined maintaining or locking the achieved orientation or alignment.
Epoxy-based locking of flexure units was proposed for passive alignment in prior art designs. However, epoxy-based locking is undesirable if the locking is irreversible. Further, it is hard to account for uniform hardening of epoxy in a confined volume and also, mismatch in thermal coefficients of expansion of the epoxy and flexure elements can result in warping and loss of alignment. In other cases, active feedback control of three degree of freedom, for example, vertical position, pitch and roll has been implemented in some previous designs. While active feedback control allows for robust alignment, they necessitate the use of multiple actuators and sensors. The overall resolution for the alignment is limited by the dynamic error performance of the sensors and the design of the control system.